To realize human-machine interaction, a number of technologies have been applied. Among them, one is floating touch, which is used in systems such as Samsung Galaxy S4. Floating touch combines the self and mutual capacitance touch sensing to detect a fingertip; however, it only has a dynamic range up to 5 cm. Another is camera hand recognition, which is used in systems such as Xbox Kinect. Camera hand recognition continuously captures images and compares hand positions of a user in different pictures so as to determine the hand motion. It requires the user to be at some minimum distance (about 60 cm) away from the system.